Materials Data on KCa4Si8O28F by Materials Project
KCa4Si8O28F crystallizes in the tetragonal P4/mnc space group. The structure is three-dimensional. K is bonded in a hexagonal bipyramidal geometry to eight equivalent O atoms. All K–O bond lengths are 2.91 Å. Ca is bonded in a 7-coordinate geometry to six O and one F atom. There are a spread of Ca–O bond distances ranging from 2.32–2.75 Å. The Ca–F bond length is 2.29 Å. Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.65 Å. There are four inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to two equivalent Si atoms. In the second O site, O is bonded in a distorted trigonal non-coplanar geometry to one K, one Ca, and one O atom. The O–O bond length is 1.27 Å. In the third O site, O is bonded in a distorted trigonal planar geometry to two equivalent Ca and one Si atom. In the fourth O site, O is bonded in a bent 150 degrees geometry to two equivalent Si atoms. F is bonded in a square co-planar geometry to four equivalent Ca atoms.